Man up.
Although I do get a bit queasy when in the passenger seat. I think it's to do with not being in control/not being able to predict the movement of the vehicle and counter as easily as when driving.
Nausia is controlled by the brain, not the guts.
Motion sickness is basically a "Safe mode" for the body. In much the same way as an engine ECU generates fault codes if some of the inputs do not match up (A common one is manifold pressure and airflow in the case of a faulty airflow meter) and puts the vehicle into "Safe Mode" to prevent further damage.
If the sensory inputs from the Eyes and ears do not match up. Your brain generates a "Fault Code" in much the same way.
Say, You are on a ship, your eyes are telling you that you are in a room, your ears are telling you that you are moving all over the place (Balance).
Or
You are playing a action video game, your ears are telling you that you are sitting in a room, your eyes are telling you that you are moving all over the place.
Because they do not correlate, Your "Body control Module" doesn't know which inputs to believe, the BCM "Software" then puts you into "Safety Mode" by making you feel ill so that you sit down to reduce the likelihood of harming yourself. It also makes you throw up in case you have eaten something poisonous.
The trick is to try to correlate your sensory inputs. In a moving vehicle you need to look out of a window at a distant fixed object or (In the case of a ship) go up on deck and stare at the horizon.
And, of course, as you point out. Being in control of the vehicle also helps.
